Air conditioner not blowing cold air even after a charge

I have a 99 Suburban with front and rear ac. It recently has stopped blowing cold air. I added 15 ozs of 134a +, up between 25 -45psi with no improvemnt. I noticed that when the compressor cycles the pressure drops below 25psi.
1. Have I recharged improperly?
2. Could there be another problem?
3. should I add more 134a +

I would appreciate any other suggestions since this was the fitst time ever I tried servicing the AC system on any vehicle. There are no other symptons on this vehicle , just lack of cold air.
Thank You
john

I have a 99 Suburban with front and rear ac. It recently has stopped blowing cold air. I added 15 ozs of 134a +, up between 25 -45psi with no improvemnt. I noticed that when the compressor cycles the pressure drops below 25psi.
1. Have I recharged improperly?
2. Could there be another problem?
3. should I add more 134a +

I would appreciate any other suggestions since this was the fitst time ever I tried servicing the AC system on any vehicle. There are no other symptons on this vehicle , just lack of cold air.
Thank You
john


with the windows open and the fan speed to max...the compressor should continue to run and not shut down or drop in pressure with the air temp @80deg. f...R 134 low side pressure should be at 40 psi...if pressure drops then rises add small amounts until pressure stabilizes....

where the refrigerent lines at fire wall go into the vehicle using your fingers feel for both lines to be at about the same cold temperature..


if these lines are not cold and the pressure is steady at 40psi at low side fill point you most likely have air in the refrigerent system....



don't forget to check the temperature door control as this can cause lack of proper temperature from vents....


if you add too much r134 you could damage compressor so with compressor running the pressure must never get above 50 psi ....

Having nearly the very same a/c problem with my 99 burb that has front and rear a/c, one small twist, the rear a/c blows cold the front a/c does not. Assuming there are check valve like assemblies, if I have air in mine, would it accumulate in the front evap? versus the rear? Doesn't seem likely to me. Do dual A/C's have two expansion valves? Perhaps a piece of trash in the expansion valve? Assumes dual a/c have two expansion valves? Do they?

check your expansion valves and/or orifice tubes. I had a problem where the system was fully charged but the back expansion valve was not functioning, so it wasn't blowing cold. The compressor should periodically turn off and on, I had a problem with another of my Suburbans where the compressor kept on running (problem with switch), and it eventually built so much pressure (I think weather also had something to do with it 125+degrees outside) that the A/C hose blew up while I was driving. So I'm thinking that it's normal for the compressor to cycle on and off.

good luck

These systems have an expansion valve in the rear- and an orifice tube just beyond the "Y" split in the front- check it. It is along side the frame rail- there is a connection right next to it to access it.

These systems have an expansion valve in the rear- and an orifice tube just beyond the "Y" split in the front- check it. It is along side the frame rail- there is a connection right next to it to access it.

Yes, orifice tube in front, expansion valve in rear. You need to read and supply BOTH low side and high side pressures to get help, at about 1500 rpm after running a few minutes.